It is really hard to recommend anything, as it sounds quite different to everything I have done. My first thought is that flood engineering must be an in demand skill set at the moment, a
quick google seems to bring up a lot of jobs. Even if you do not feel confident going for the jobs with the skills you have, perhaps you could approach the companies and see what they could offer. When you have
Assistant Flood Risk Engineer paying only £29,000- £33,000 in London I find it hard to believe they can be that picky at the moment.
That's higher than any salary I've had. I was on ~£26,000-27,000 in 2016-2017 and £23,000 in 2018 (that one was more demanding of course). I assume that people at at my earlier pay grade with London weighting are paid about as much as in that advert. I've missed the recent inflation, but I don't expect anything above £30,000; my CV has a job on it between 2018 and now, but I'm not prepared to talk about it, because I get very little work from that company and what I do get is door to door deliveries and the occasional document reformating. I honestly think I could have better chances if I ditched flood risk, planning and developer PR for something new. I think have a plausible motive. Remember Graeber's bullfeathers jobs? I'm in the "goon" sector. That sounds like justification for a career change to me (as opposed the real reason, which is that my career ended four years ago).
The trouble with those jobs is that I've never done a flood risk assessment, I had about three hours to use Microdrainage* and I worked for the Environment Agency, which deals with river and coastal flooding rather than surface water flooding (that's the local authorities). The types of jobs for which
they paid my tuition fees involved
reviewing flood risk assessments, but they didn't give a toss about that in the interviews, so I did very little flood risk work of any kind. I signed up with a small agency that specialises in that field and was recommended by my university (Penguin) and they weren't interested. At least the planning consultancy keeps in touch, even if the jobs they me tell about are too senior.
I should say that I chose to study flood risk engineering specifically because the degree was sponsored and attached to an internship. Now that I have money, I could pay for myself which broadens my options. Perhaps a tertiary college course would be more suitable, but don't hear of "mature students" attending those (I'm 31 and I studied for GCSEs, A-Levels, a BSc, then an FdSc [that's two years of a BSc]).
*The university didn't have a licence to install it on computers in the usual way. Instead, an employee of company that made Microdrainage led a couple of classes in which we used a demo to produce some data, which we then wrote up into a surface water drainage scheme in our free time. Whereas we could actually practise using ArcGIS and AutoCAD on campus desktops or using student's licences on our own computers.